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MG TD TF 1500 - Valve stem seals yes again

Hello all, I am a new kid on the block here. I have been reading the BBS and archives regarding my problem, and I am really impressed and thankful to all of you sharing your knowledge and advice. I have TF 1500 and have blue tinged white smoke at start up and after idling for a while. It seems to go away when driving. It sounds like from my reading, a valve stem seals issue. I did a compression test with a good battery and carbs wide open. I also adjusted valves before the test.
Results:
Dry: 140 135 128 135
Wet: 150 150 138 145
My engine has 60,000 miles on it, and it hasn't been touched, as per previous owner.
I would appreciate your help to check my thinking. I think I should start with replacing valve stem seals.
Questions:
1. Does this compression indicate my rings are still ok?
2. To do valve stem seals what should I replace them with?
3. Am I missing something?
Thanks in advance, Bob.
RDH Hawkins

Bob.
If it was my car I would suggest that you drive it. Then establish how much oil you are using. Your compresion figures appear to be well within limits.
Remember the MOTTO
USE-ENJOY but PRESERVE. Do not change the sequence and you will have many years of enjoyment.
Sandy
Sanders

Your valve guides are almost certainly showing some wear, but from the symptoms are not desperate for replacement yet - it depends how fussy you are. The original O ring type valve seals are not very effective, and many replace them, inlet valves only, with a modern lip seal during a cylinder head refurb. As suggested, drive it a while and you'll know when you are ready to refurb it.
Dave H
Dave Hill

Dave

why change to lip seals only for inlet? Is it because outlet doesn't suck?
W_Mueller

The exhaust side needs more lubrication than the inlet side.
Dave H
Dave Hill

Does that depend on bronze or cast iron?
W_Mueller

I wouldn't want to risk either.
Dave H
Dave Hill

Dave, what is the "modern lip seal" you refer to? Is that the Felpro? I found Stafford's article where he suggests the Felpro.
Bob
RDH Hawkins

I think those seals go under various names, and Felpro is probably one of them. You need to dig in the archives to get the background because I think some other mods are advised at the same time. I bought a set but won't fit them until I have other work to do on the head at the same time.
Dave H
Dave Hill

the lip seals are only a help on worn valves and guides. On an unworn guide the "O" ring prevents oil dripping down the stem from the split collets but must be fitted correctly. The shield under the cap prevents excessive oil getting to the valve from the side. This shield must be removed if fitting lip seals.
I have also found that the lip seal can come off and get chewed up if a groove is not cut around the guide to seat it.
Ray TF 2884
Ray Lee

Much as I thought, though I couldn't remember the detail without looking it up. The shield would be easy to remove as its relatively thin metal, but cutting a groove around the guide would be more difficult if not fitting new guides. Somebody on here claimed to have done it in situ with a Dremel.
Dave H
Dave Hill

For whatever reason our local machine shop which does about 25 plus XPAGs a year doesn’t recommend the bronze guides for our engines. They just don’t seem to hold up well. They highly recommend continuing the use of the steel guides for longevity they do not put seals on the exhaust valves to provide lubrication. I use Ford style umbrella seals on the intakes.

Bill Chasser
TD-4834
W A Chasser

Hi Bob,

Go for a run in the car then remove the rocker cover. Look at the washer shaped valve collet retainers. There is a dip in the centre where the valve stem and collets fit. These will be full of oil. Have a further look in the morning and if the oil has drained from any of them the stem seals are faulty.

Jan T
J Targosz

My head has just come back from a well known tuner ( no problems)
With instructions to ditch the top hats and fit the 8No seals he provided What is correct please?? Inlets only or inlets and exhausts
For info all new bronze guides and grooved for the seals
John
J A Davies

I believe that bronze guides require more care in terms of the clearance between valve stem and guide. Without knowing this I used them once, to my regret, on a TR engine. On any subject like this you will get differing opinions. Susceptibility to failure may depend on the exact choice of materials for valve and guide, and different engine builders / tuners will have different preferences for each, so they may have perfectly valid reasons for going one way or the other. Not having that level of knowledge can lead us to think one or the other is wrong, but not so. If your well known tuner has lots of experience with xpag engines I would follow his advice.
Dave H
Dave Hill

Dave
Many thanks
J A Davies

I've put together a dozen heads in the past 2 years, and have had no problems with bronze guides on the exhaust side. I do have them opened out a bit more that usual - I use .002" more than standard - and have had no problems with stuck valves, or excessive oil consumption. I use the stock o-rings.

Tom Lange
MGT Repair
t lange

Just checked and the valve stem oil seals commonly used are from Mini 1275, Metro, Marina and other A series engines (BMC, BMH, Austin Rover, etc).
Dave H
Dave Hill

In the original set up there is a circular shroud that fits inside the spring and slides over the outside of the guide. This prevents oil splash against the stem of the valve. To supplement this a small O ring is fitted under the collets to stop oil running down the stem. When modern seals are fitted the shrouds have to be removed and if the seals fail there is no protection from oil spray. Despite my TF having had a rebore, new pistons and new guides it still left a trail of blue smoke. The reason was entirely my fault. I, as many others have done, fitted the O rings onto the valve stems rather than under the collets. I reasoned that Mini seals were from a later engine so must be better than the originals so fitted them to the inlets. These do have a lip on the inside and need a small groove near the top of the guide to prevent them lifting. I considered making up a tool to do this in situ, or even filing them with a needle file but eventually pressed the guides out and turned the grooves in my Myford lathe. This of course messed up my Serdi precision cut seats but I simply sorted them them with good old fashioned grinding paste. I must report that the Mini seals have totally cured the smoke problem.

Jan T
J Targosz

Thanks to all for the wealth of knowledge! Jan, I am still going to take a spin and remove valve cover as suggested. You mentioned the "circular shroud". I have found the "o" rings from Moss, but I don't see the shrouds you mentioned listed. Are they available somewhere? Im going to attack this without removing the head. I've read the archives on ways of doing this, so I think I will give it a go. What's wrong with my thinking of staying original and then when I need to do more work on engine considering the other alternatives?
Bob
RDH Hawkins

Hi Bob,

Go to the Brown and Gammons UK site, TD & TF, Engine Spares, valves and Guides. The shroud is No 33. They are VERY expensive - £8 each!

Cheers

Jan
J Targosz

Bob,
with 60000 mile your engine probably still has the original shrouds fitted.
If you have a workshop manual you can see them in fig A21 section A28.
Ray TF 2884 (marked oil shield)

Ray Lee

If you fit the "O" seals you need to compress the springs before fitting the rings.
"O" rings do not like fingernails, I cut a section of mastic cone at 8mm chamfer the inside and slide the ring over the stem and into the groove.
Ray TF 2884
Ray Lee

Ray
First class advice I would never have thought of that
Thanks
John
J A Davies

John,
45 years of ownership have taught me to find an easy way for everything. Plus this site has had many people post and get me out of a mess.
Ray
Ray Lee

@Tom

did you open only the exhaust guides a bit more than standard?

W_Mueller

All of them.
Dave H
Dave Hill

Nothing beats a good stem seal story
I use standard "O" rings, no shrouds and chamfered guides---never had a problem--
I believe the secret is to chamfer or round the top of the guide to stop oil pooling there waiting to get sucked in-I've actually seen new guides with concave tops---???
To test if the 'original type' seals (O rings)are ok--squirt some oil on the top of the spring caps forming a pool up against the stems--then recheck in an hour or so, if the oil has drained away down through the gap between the keepers the seals are faulty--
If the oil is still there the seals are ok
If they have been fitted properly it's unusual for them to fail
willy
William Revit

Willy, the main problem is people fitting the "o" rings before putting on the springs. As the caps are compressed the shrouds hit the rings and damage them. See my earlier comment about a cone guide to install. I have bronze guides with excess clearance and have no problems with the original set-up.
Also for anybody fitting modern seals, you still need the "o" rings to fill the gap, I have seen some bad "chatter" marks on engines without this.
Ray TF 2884
Ray Lee

I use positive stop Teflon valve stem seals, the guide does need to be machined to fit them, without the deflector.
Len Fanelli

Ray
Yep I agree
I use a split milkshake plastic straw ( after I've had the milkshake)
Push the springs and cap asy. down , slide the O ring down the straw over the stem fit the keepers and release the spring back up against the seal/keepers---i have found it pays to lube the seal, it goes on easier and the cap comes up on it holding the keepers tighter as well otherwise sometimes if the O ring is a bit on the firm side the cap can be hampered a bit squooshing it up leaving the keepers a bit on the loose side till it all settles down in place
willy
William Revit

I just remembered Colin Stafford's write-up on this topic in Ttalk, see http://www.ttalk.info/StaffordSeal.htm Bud
Bud Krueger

This thread was discussed between 23/10/2018 and 03/11/2018

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